Icing condition detection system

1. An apparatus comprising:

a first piezoelectric material having a first surface proximate to a surface of a vehicle and configured to vibrate in a shear mode wherein the first piezoelectric material vibrates in a direction perpendicular to a direction in which waves generated by the first piezoelectric material propagate;

a second piezoelectric material having a second surface remote from the surface of the vehicle and configured to vibrate in the shear mode;

a vibration detector configured to detect a difference in a frequency of vibrations in the first piezoelectric material compared to a frequency of vibrations in the second piezoelectric material to detect a presence of an icing condition on the first surface of the first piezoelectric material; and

an electrical resistive heater configured to remove ice from the surface of the vehicle.

2. The apparatus of claim 1 , wherein the first piezoelectric material and the vibration detector form a piezoelectric sensor.

3. The apparatus of claim 1 further comprising:

a vibration generator configured to cause the first piezoelectric material to vibrate.

4. The apparatus of claim 1 , wherein the first piezoelectric material and the vibration detector are associated with a housing installed in the vehicle such that the first surface of the first piezoelectric material is flush with the surface of the vehicle.

5. The apparatus of claim 1 , wherein in being configured to detect the difference in the frequency of vibrations in the first piezoelectric material that indicates the presence of the icing condition on the surface of the first piezoelectric material, the vibration detector is configured to detect a number of icing conditions on the surface of the first piezoelectric material based on a change in the vibrations.

6. The apparatus of claim 1 further comprising:

an anti-icing system configured to remove ice from the first surface of the first piezoelectric material.

7. The apparatus of claim 1 , wherein:

the first surface of the first piezoelectric material is exposed to an environment;

the second surface of the second piezoelectric material is not exposed to the environment; and

the second piezoelectric material is identical to the first piezoelectric material.

8. The apparatus of claim 7 , wherein the first piezoelectric material and the second piezoelectric material are exposed to a same temperature, wherein changes in the temperature result in vibrations in the first piezoelectric material being the same as the vibrations in the second piezoelectric material when ice or other fluid is not present on the surface of the first piezoelectric material, and wherein the vibration detector is further configured to detect a change in the frequency of vibration of the first piezoelectric material relative to a frequency of vibration of the second piezoelectric material to indicate the presence of the icing condition on the surface of the first piezoelectric material.

9. The apparatus of claim 1 , wherein the icing condition is selected from at least one of ice on the surface of the vehicle and water droplets on the surface of the vehicle in conditions that cause the water droplets to form the ice.

10. An apparatus comprising:

a first piezoelectric material having a first surface proximate to a surface of a vehicle and configured to vibrate in a shear mode wherein the piezoelectric material vibrates in a direction perpendicular to a direction in which waves generated by the first piezoelectric material propagate;

a second piezoelectric material having a second surface remote from the surface of the vehicle and configured to vibrate in the shear mode;

a vibration detector configured to detect a difference in vibrations in a frequency of vibration of the first piezoelectric material compared to a frequency of vibration of the second piezoelectric material to indicate a presence of ice on the first surface of the first piezoelectric material; and

an electrical resistive heater configured to remove the ice from the surface of the vehicle.

11. An apparatus comprising:

a first piezoelectric material having a first surface proximate to a surface of a vehicle such that the first surface is exposed to an environment, wherein the first piezoelectric material is configured to vibrate in a shear mode wherein the first piezoelectric material vibrates in a direction perpendicular to a direction in which waves generated by the first piezoelectric material propagate;

a second piezoelectric material having a second surface remote from the surface of the vehicle, wherein the second piezoelectric material is configured to vibrate in the shear mode at a second frequency;

a vibration generator configured to detect a difference in the first frequency and the second frequency to indicate a presence of an icing condition on the first surface of the first piezoelectric material; and

an electrical resistive heater configured to remove ice from the surface of the vehicle.

12. The apparatus of claim 11 , wherein the first piezoelectric material and the second piezoelectric material are exposed to a same temperature.

13. The apparatus of claim 11 , wherein the vibrations in the second piezoelectric material define reference vibrations.

14. The apparatus of claim 11 , wherein the icing condition is selected from at least one of ice on the surface of the vehicle and water droplets on the surface of the vehicle in conditions that cause the water droplets to form the ice.

15. The apparatus of claim 14 , wherein the icing condition comprises the ice on the surface of the vehicle and the vibration generator is further configured to determine an amount of the ice developed on the surface of the vehicle.

16. The apparatus of claim 11 , wherein the first piezoelectric material is the same as the second piezoelectric material.

17. The apparatus of claim 11 , wherein the first piezoelectric material and the second piezoelectric material are associated with a housing installed on the vehicle such that the first surface of the first piezoelectric material is flush with a surface of the vehicle and the second surface of the second piezoelectric material is recessed within the housing.

18. The apparatus of claim 11 , wherein the first piezoelectric material vibrates in the shear mode such that the first piezoelectric material vibrates in a direction perpendicular to a direction in which waves generated by the first piezoelectric material propagate.